At 3am on Saturday, soldiers ran a checkpoint behind the Tesco Lotus hypermarket and stopped a black Toyota pickup truck with two men inside the truck, they acted suspiciously but nothing illegal was found in the vehicle.

Colonel Kidakorn said the authorities did not find any illegal items in the truck but they noticed that the brothers appeared nervous and had given conflicting accounts of why they were out driving at an unusual hour. This prompted the order to search the forest nearby, where the drugs were uncovered.

The men would be released if no evidence could be found to link them to the drugs, Kidakorn added.

Meanwhile, Two suspects were arrested and over one million amphetamine pills and 2kg of crystal methamphetamine were seized by the Narcotic Suppression Bureau (NSB) on Wednesday night.

Pol Maj Gen Tanai Apichartseni, an NSB officer, said an intelligence source informed them that a drug trafficking ring was going to smuggle large amounts of illicit drugs from Chiang Rai through Nakhon Sawan to Bangkok, using a pickup, with a licence plate registered in Phitsanulok province, as the mode of transport.

Checking cameras, they were able to spot the suspected vehicle while driving through Chiang Rai.

On Wednesday evening, the investigators were able to track down the vehicle, parked close by the Khao Thong Toyota Centre and an antique store in Phtisanulok province.

The police identified themselves and asked to investigate the pickup.

Inside the vehicle, the police found eight bags containing 1.27 million amphetamine pills and 2kg of crystal methamphetamine.

The suspects arrested were identified as Phichet Hoethongphet, 32, and Phichit Saehoe, 21. Both suspects and the seized property were taken into NSB custody and will later be prosecuted.